[v2] rtc: ds1307: generalise ram size and offset

From: Austin Boyle <Austin.Boyle@aviatnet.com>

This patch generalises NVRAM to support RAM with other size and offset, such
as the 64 bytes of SRAM on the mcp7941x.

Cc: Wolfram Sang <w.sang@pengutronix.de>
Cc: David Anderson <danders.dev@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Austin Boyle <Austin.Boyle@aviatnet.com>
---
this patch is based on Wolfram Sang's tree:
git://git.pengutronix.de/git/wsa/linux-2.6.git ds1307

patch depends on:
rtc: ds1307: comment and format cleanup 21af5f7bd6
rtc: ds1307: simplify irq setup code  8c63e03627
rtc: ds1307: refactor chip_desc table e246db081d
rtc: add initial support for mcp7941x parts e69bba2d3a

On Thu, Nov 03, 2011 at 12:33:54PM +1300, Austin Boyle wrote:
> From: Austin Boyle <Austin.Boyle@aviatnet.com>
> 
> This patch generalises NVRAM to support RAM with other size and offset, such
> as the 64 bytes of SRAM on the mcp7941x.

Thanks! This made the patch much more readable, so I saw another optimization.
And one question.

> 
> Cc: Wolfram Sang <w.sang@pengutronix.de>
> Cc: David Anderson <danders.dev@gmail.com>
> Cc: Alessandro Zummo <a.zummo@towertech.it>
> Cc: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
> Signed-off-by: Austin Boyle <Austin.Boyle@aviatnet.com>
> ---
> this patch is based on Wolfram Sang's tree:
> git://git.pengutronix.de/git/wsa/linux-2.6.git ds1307
> 
> patch depends on:
> rtc: ds1307: comment and format cleanup 21af5f7bd6
> rtc: ds1307: simplify irq setup code  8c63e03627
> rtc: ds1307: refactor chip_desc table e246db081d
> rtc: add initial support for mcp7941x parts e69bba2d3a
> 
> --- a/drivers/rtc/rtc-ds1307.c	2011-10-10 11:22:22.674690998 +1300
> +++ b/drivers/rtc/rtc-ds1307.c	2011-11-03 12:17:40.777642801 +1300
> @@ -104,6 +104,8 @@ enum ds_type {
>  
>  struct ds1307 {
>  	u8			offset; /* register's offset */
> +	u16			nvram_offset;
> +	u16			nvram_size;
>  	u8			regs[11];
>  	enum ds_type		type;
>  	unsigned long		flags;
> @@ -119,19 +121,19 @@ struct ds1307 {
>  };
>  
>  struct chip_desc {
> -	unsigned		nvram56:1;
> +	unsigned		nvram:1;

What about removing this field...

>  	unsigned		alarm:1;
>  };
>  
>  static const struct chip_desc chips[last_ds_type] = {
>  	[ds_1307] = {
> -		.nvram56	= 1,
> +		.nvram		= 1,
>  	},
>  	[ds_1337] = {
>  		.alarm		= 1,
>  	},
>  	[ds_1338] = {
> -		.nvram56	= 1,
> +		.nvram		= 1,
>  	},
>  	[ds_1339] = {
>  		.alarm		= 1,
> @@ -139,6 +141,9 @@ static const struct chip_desc chips[last
>  	[ds_3231] = {
>  		.alarm		= 1,
>  	},
> +	[mcp7941x] = {
> +		.nvram		= 1,
> +	},
>  };
>  
>  static const struct i2c_device_id ds1307_id[] = {
> @@ -543,8 +548,6 @@ static const struct rtc_class_ops ds13xx
>  
>  /*----------------------------------------------------------------------*/
>  
> -#define NVRAM_SIZE	56
> -
>  static ssize_t
>  ds1307_nvram_read(struct file *filp, struct kobject *kobj,
>  		struct bin_attribute *attr,
> @@ -557,14 +560,15 @@ ds1307_nvram_read(struct file *filp, str
>  	client = kobj_to_i2c_client(kobj);
>  	ds1307 = i2c_get_clientdata(client);
>  
> -	if (unlikely(off >= NVRAM_SIZE))
> +	if (unlikely(off >= ds1307->nvram_size))
>  		return 0;
> -	if ((off + count) > NVRAM_SIZE)
> -		count = NVRAM_SIZE - off;
> +	if ((off + count) > ds1307->nvram_size)
> +		count = ds1307->nvram_size - off;
>  	if (unlikely(!count))
>  		return count;
>  
> -	result = ds1307->read_block_data(client, 8 + off, count, buf);
> +	result = ds1307->read_block_data(client, ds1307->nvram_offset + off,
> +								count, buf);
>  	if (result < 0)
>  		dev_err(&client->dev, "%s error %d\n", "nvram read", result);
>  	return result;
> @@ -582,14 +586,15 @@ ds1307_nvram_write(struct file *filp, st
>  	client = kobj_to_i2c_client(kobj);
>  	ds1307 = i2c_get_clientdata(client);
>  
> -	if (unlikely(off >= NVRAM_SIZE))
> +	if (unlikely(off >= ds1307->nvram_size))
>  		return -EFBIG;
> -	if ((off + count) > NVRAM_SIZE)
> -		count = NVRAM_SIZE - off;
> +	if ((off + count) > ds1307->nvram_size)
> +		count = ds1307->nvram_size - off;
>  	if (unlikely(!count))
>  		return count;
>  
> -	result = ds1307->write_block_data(client, 8 + off, count, buf);
> +	result = ds1307->write_block_data(client, ds1307->nvram_offset + off,
> +								count, buf);
>  	if (result < 0) {
>  		dev_err(&client->dev, "%s error %d\n", "nvram write", result);
>  		return result;
> @@ -605,7 +610,6 @@ static struct bin_attribute nvram = {
>  
>  	.read	= ds1307_nvram_read,
>  	.write	= ds1307_nvram_write,
> -	.size	= NVRAM_SIZE,
>  };
>  
>  /*----------------------------------------------------------------------*/
> @@ -692,6 +696,9 @@ static int __devinit ds1307_probe(struct
>  		break;
>  
>  	case rx_8025:
> +		ds1307->nvram_size = 64; /* 64 bytes SRAM */
> +		ds1307->nvram_offset = 0x20;
> +

Question: Why are you adding this code here and not to the mcp7941x related
code?

>  		tmp = i2c_smbus_read_i2c_block_data(ds1307->client,
>  				RX8025_REG_CTRL1 << 4 | 0x08, 2, buf);
>  		if (tmp != 2) {
> @@ -758,6 +765,8 @@ static int __devinit ds1307_probe(struct
>  		break;
>  	case ds_1388:
>  		ds1307->offset = 1; /* Seconds starts at 1 */
> +		ds1307->nvram_size = 56; /* 56 bytes NVRAM */
> +		ds1307->nvram_offset = 8;

Is this the right place to enable it for the 1307/1338?

>  		break;
>  	default:
>  		break;
> @@ -893,11 +902,12 @@ read_rtc:
>  		dev_dbg(&client->dev, "got IRQ %d\n", client->irq);
>  	}
>  
> -	if (chip && chip->nvram56) {
> +	if (chip && chip->nvram) {

If we removed the nvram field above, then we could simply use
ds1307->nvram_size here. If that turns out to be too messy to set up, we could
also put nvram_size and nvram_offset to the chip_desc instead.

> +		nvram.size = ds1307->nvram_size;
>  		err = sysfs_create_bin_file(&client->dev.kobj, &nvram);
>  		if (err == 0) {
>  			set_bit(HAS_NVRAM, &ds1307->flags);
> -			dev_info(&client->dev, "56 bytes nvram\n");
> +			dev_info(&client->dev, "%zd bytes nvram\n", nvram.size);
>  		}
>  	}
>  
>

On Thu, 2011-11-03 at 08:46 +0100, Wolfram Sang wrote:
> 
> If we removed the nvram field above, then we could simply use
> ds1307->nvram_size here. If that turns out to be too messy to set up, we could
> also put nvram_size and nvram_offset to the chip_desc instead.

Thanks for the quick reply. I like this idea. What about adding offset,
nvram_offset and nvram_size to the chip description? This would make it
easier to add support for other chips, without having to modify one of
the switch statements in probe. Patch follows.

Cheers,
Austin.